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</div>
<div class="section">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="bbv2.tutorial"></a>Tutorial</h2></div></div></div>
<div class="toc"><dl>
<dt><span class="section"><a href="tutorial.html#bbv2.tutorial.hello">Hello, world</a></span></dt>
<dt><span class="section"><a href="tutorial.html#bbv2.tutorial.properties">Properties</a></span></dt>
<dt><span class="section"><a href="tutorial.html#bbv2.tutorial.hierarchy">Project Hierarchies</a></span></dt>
<dt><span class="section"><a href="tutorial.html#bbv2.tutorial.libs">Dependent Targets</a></span></dt>
<dt><span class="section"><a href="tutorial.html#bbv2.tutorial.linkage">Static and shared libaries</a></span></dt>
<dt><span class="section"><a href="tutorial.html#bbv2.tutorial.conditions">Conditions and alternatives</a></span></dt>
<dt><span class="section"><a href="tutorial.html#bbv2.tutorial.prebuilt">Prebuilt targets</a></span></dt>
</dl></div>
<p>
    This section will guide you though the most basic features of Boost.Build
    V2. We will start with the &#8220;Hello, world&#8221; example, learn how
    to use libraries, and finish with testing and installing features.
  </p>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="bbv2.tutorial.hello"></a>Hello, world</h3></div></div></div>
<p>
      The simplest project that Boost.Build can construct is stored in
      <code class="filename">example/hello/</code> directory. The project is described by
      a file called <code class="filename">Jamroot</code> that contains:

</p>
<pre class="programlisting">
exe hello <span class="special">:</span> hello.cpp <span class="special">;</span>
</pre>
<p>

      Even with this simple setup, you can do some interesting things. First of
      all, just invoking <span class="command"><strong>b2</strong></span> will build the <code class="filename">hello
      </code> executable by compiling and linking <code class="filename">hello.cpp
      </code>. By default, the debug variant is built. Now, to build the release
      variant of <code class="filename">hello</code>, invoke

</p>
<pre class="screen">
b2 release
</pre>
<p>

      Note that the debug and release variants are created in different directories,
      so you can switch between variants or even build multiple variants at
      once, without any unnecessary recompilation. Let us extend the example by
      adding another line to our project's <code class="filename">Jamroot</code>:

</p>
<pre class="programlisting">
exe hello2 <span class="special">:</span> hello.cpp <span class="special">;</span>
</pre>
<p>

      Now let us build both the debug and release variants of our project again:

</p>
<pre class="screen">
b2 debug release
</pre>
<p>

      Note that two variants of <code class="filename">hello2</code> are linked. Since we
      have already built both variants of <code class="filename">hello</code>, hello.cpp
      will not be recompiled; instead the existing object files will just be
      linked into the corresponding variants of <code class="filename">hello2</code>. Now
      let us remove all the built products:

</p>
<pre class="screen">
b2 --clean debug release
</pre>
<p>

      It is also possible to build or clean specific targets. The following two
      commands, respectively, build or clean only the debug version of
      <code class="filename">hello2</code>.

</p>
<pre class="screen">
b2 hello2
b2 --clean hello2
</pre>
<p>
    </p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="bbv2.tutorial.properties"></a>Properties</h3></div></div></div>
<div class="toc"><dl>
<dt><span class="section"><a href="tutorial.html#bbv2.tutorial.properties.requirements">Build Requests and Target Requirements</a></span></dt>
<dt><span class="section"><a href="tutorial.html#bbv2.tutorial.properties.project_attributes">Project Attributes</a></span></dt>
</dl></div>
<p>
      To represent aspects of target configuration such as
      debug and release variants, or single- and multi-threaded
      builds portably, Boost.Build uses <em class="firstterm">features</em> with
      associated <em class="firstterm">values</em>.  For
      example, the <code class="computeroutput">debug-symbols</code> feature can have a value of <code class="computeroutput">on</code> or
      <code class="computeroutput">off</code>.  A <em class="firstterm">property</em> is just a (feature,
      value) pair.  When a user initiates a build, Boost.Build
      automatically translates the requested properties into appropriate
      command-line flags for invoking toolset components like compilers
      and linkers.
    </p>
<p>
      There are many built-in features that can be combined to
      produce arbitrary build configurations.  The following command
      builds the project's <code class="computeroutput">release</code> variant with inlining
      disabled and debug symbols enabled:
</p>
<pre class="screen">
b2 release inlining=off debug-symbols=on
</pre>
<p>
    </p>
<p>
      Properties on the command-line are specified with the syntax:

</p>
<pre class="screen">
<em class="replaceable"><code>feature-name</code></em>=<em class="replaceable"><code>feature-value</code></em>
</pre>
<p>
    </p>
<p>
      The <code class="option">release</code> and <code class="option">debug</code> that we have seen
      in <span class="command"><strong>b2</strong></span> invocations are just a shorthand way to specify
      values of the <code class="varname">variant</code> feature.  For example, the
      command above could also have been written this way:

      </p>
<pre class="screen">
b2 variant=release inlining=off debug-symbols=on
      </pre>
<p>
    </p>
<p>
      <code class="varname">variant</code> is so commonly-used that it has been given
      special status as an <em class="firstterm">implicit</em> feature&#8212;
      Boost.Build will deduce its identity just from the name of one of its
      values.
    </p>
<p>
      A complete description of features can be found in <a class="xref" href="reference.html#bbv2.reference.features" title="Features and properties">the section called &#8220;Features and properties&#8221;</a>.
    </p>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="bbv2.tutorial.properties.requirements"></a>Build Requests and Target Requirements</h4></div></div></div>
<p>
        The set of properties specified on the command line constitutes
        a <em class="firstterm">build request</em>&#8212;a description of
        the desired properties for building the requested targets (or,
        if no targets were explicitly requested, the project in the
        current directory). The <span class="emphasis"><em>actual</em></span>
        properties used for building targets are typically a
        combination of the build request and properties derived from
        the project's <code class="filename">Jamroot</code> (and its other
        Jamfiles, as described in <a class="xref" href="tutorial.html#bbv2.tutorial.hierarchy" title="Project Hierarchies">the section called &#8220;Project Hierarchies&#8221;</a>). For example, the
        locations of <code class="computeroutput">#include</code>d header files are normally
        not specified on the command-line, but described in
        Jamfiles as <em class="firstterm">target
        requirements</em> and automatically combined with the
        build request for those targets. Multithread-enabled
        compilation is another example of a typical target
        requirement. The Jamfile fragment below
        illustrates how these requirements might be specified.
      </p>
<pre class="programlisting">
exe hello
    <span class="special">:</span> hello.cpp
    <span class="special">:</span> &lt;include&gt;boost &lt;threading&gt;multi
    <span class="special">;</span>
</pre>
<p>
        When <code class="filename">hello</code> is built, the two requirements specified
        above will always be present. If the build request given on the
        <span class="command"><strong>b2</strong></span> command-line explictly contradicts a target's
        requirements, the target requirements usually override (or, in the case
        of &#8220;free&#8221;&#8221; features like
        <code class="varname">&lt;include&gt;</code>,
        <sup>[<a name="idp211870528" href="#ftn.idp211870528" class="footnote">13</a>]</sup>
        augments) the build request.
      </p>
<div class="tip"><table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Tip]" src="../../../doc/src/images/tip.png"></td>
<th align="left">Tip</th>
</tr>
<tr><td align="left" valign="top"><p>
          The value of the <code class="varname">&lt;include&gt;</code> feature is
          relative to the location of <code class="filename">Jamroot</code> where it is
          used.
        </p></td></tr>
</table></div>
</div>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="bbv2.tutorial.properties.project_attributes"></a>Project Attributes</h4></div></div></div>
<p>
        If we want the same requirements for our other target,
        <code class="filename">hello2</code>, we could simply duplicate them. However,
        as projects grow, that approach leads to a great deal of repeated
        boilerplate in Jamfiles.

        Fortunately, there's a better way. Each project can specify a set of
        <em class="firstterm">attributes</em>, including requirements:

</p>
<pre class="programlisting">
project
    <span class="special">:</span> requirements &lt;include&gt;/home/ghost/Work/boost &lt;threading&gt;multi
    <span class="special">;</span>

exe hello <span class="special">:</span> hello.cpp <span class="special">;</span>
exe hello2 <span class="special">:</span> hello.cpp <span class="special">;</span></pre>
<p>

        The effect would be as if we specified the same requirement for both
        <code class="filename">hello</code> and <code class="filename">hello2</code>.
      </p>
</div>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="bbv2.tutorial.hierarchy"></a>Project Hierarchies</h3></div></div></div>
<p>
      So far we have only considered examples with one project, with
      one user-written Boost.Jam file, <code class="filename">Jamroot</code>. A typical
      large codebase would be composed of many projects organized into a tree.
      The top of the tree is called the <em class="firstterm">project root</em>.
      Every subproject is defined by a file called <code class="filename">Jamfile</code>
      in a descendant directory of the project root. The parent project of a
      subproject is defined by the nearest <code class="filename">Jamfile</code> or
      <code class="filename">Jamroot</code> file in an ancestor directory. For example,
      in the following directory layout:

</p>
<pre class="screen">
top/
  |
  +-- Jamroot
  |
  +-- app/
  |    |
  |    +-- Jamfile
  |    `-- app.cpp
  |
  `-- util/
       |
       +-- foo/
       .    |
       .    +-- Jamfile
       .    `-- bar.cpp
</pre>
<p>

      the project root is <code class="filename">top/</code>. The projects in
      <code class="filename">top/app/</code> and <code class="filename">top/util/foo/</code> are
      immediate children of the root project.

      </p>
<div class="note"><table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../doc/src/images/note.png"></td>
<th align="left">Note</th>
</tr>
<tr><td align="left" valign="top"><p>
          When we refer to a &#8220;Jamfile,&#8221; set in normal
          type, we mean a file called either
          <code class="filename">Jamfile</code> or
          <code class="filename">Jamroot</code>.  When we need to be more
          specific, the filename will be set as
          &#8220;<code class="filename">Jamfile</code>&#8221; or
          &#8220;<code class="filename">Jamroot</code>.&#8221;
        </p></td></tr>
</table></div>
<p>
    </p>
<p>
      Projects inherit all attributes (such as requirements)
      from their parents.  Inherited requirements are combined with
      any requirements specified by the subproject.
      For example, if <code class="filename">top/Jamroot</code> has

</p>
<pre class="programlisting">
&lt;include&gt;/home/ghost/local
</pre>
<p>

      in its requirements, then all of its subprojects will have it
      in their requirements, too.  Of course, any project can add
      include paths to those specified by its parents. <sup>[<a name="idp211886336" href="#ftn.idp211886336" class="footnote">14</a>]</sup>
    More details can be found in
      <a class="xref" href="overview.html#bbv2.overview.projects" title="Projects">the section called &#8220;Projects&#8221;</a>.
    </p>
<p>
      Invoking <span class="command"><strong>b2</strong></span> without explicitly specifying
      any targets on the command line builds the project rooted in the
      current directory.  Building a project does not automatically
      cause its subprojects to be built unless the parent project's
      Jamfile explicitly requests it. In our example,
      <code class="filename">top/Jamroot</code> might contain:

</p>
<pre class="programlisting">
build-project app <span class="special">;</span>
</pre>
<p>

      which would cause the project in <code class="filename">top/app/</code>
      to be built whenever the project in <code class="filename">top/</code> is
      built. However, targets in <code class="filename">top/util/foo/</code>
      will be built only if they are needed by targets in
      <code class="filename">top/</code> or <code class="filename">top/app/</code>.
    </p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="bbv2.tutorial.libs"></a>Dependent Targets</h3></div></div></div>
<p>
      When building a target <code class="filename">X</code> that depends on first
      building another target <code class="filename">Y</code> (such as a
      library that must be linked with <em class="firstterm">X</em>),
      <code class="filename">Y</code> is called a
      <em class="firstterm">dependency</em> of <code class="filename">X</code> and
      <code class="filename">X</code> is termed a
      <em class="firstterm">dependent</em> of <code class="filename">Y</code>.
    </p>
<p>To get a feeling of target dependencies, let's continue the
      above example and see how <code class="filename">top/app/Jamfile</code> can
      use libraries from <code class="filename">top/util/foo</code>.  If
      <code class="filename">top/util/foo/Jamfile</code> contains

</p>
<pre class="programlisting">
lib bar <span class="special">:</span> bar.cpp <span class="special">;</span>
</pre>
<p>

      then to use this library in <code class="filename">top/app/Jamfile</code>, we can
      write:

</p>
<pre class="programlisting">
exe app <span class="special">:</span> app.cpp ../util/foo//bar <span class="special">;</span>
</pre>
<p>

      While <code class="computeroutput">app.cpp</code> refers to a regular source file,
      <code class="computeroutput">../util/foo//bar</code> is a reference to another target:
      a library <code class="filename">bar</code> declared in the Jamfile at
      <code class="filename">../util/foo</code>.
    </p>
<div class="tip"><table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Tip]" src="../../../doc/src/images/tip.png"></td>
<th align="left">Tip</th>
</tr>
<tr><td align="left" valign="top"><p>Some other build system have special syntax for listing dependent
      libraries, for example <code class="varname">LIBS</code> variable. In Boost.Build,
      you just add the library to the list of sources.
      </p></td></tr>
</table></div>
<p>Suppose we build <code class="filename">app</code> with:
    </p>
<pre class="screen">
b2 app optimization=full define=USE_ASM
    </pre>
<p>
    Which properties will be used to build <code class="computeroutput">foo</code>? The answer is
    that some features are
    <em class="firstterm">propagated</em>&#8212;Boost.Build attempts to use
    dependencies with the same value of propagated features. The
    <code class="varname">&lt;optimization&gt;</code> feature is propagated, so both
    <code class="filename">app</code> and <code class="filename">foo</code> will be compiled
    with full optimization. But <code class="varname">&lt;define&gt;</code> is not
    propagated: its value will be added as-is to the compiler flags for
    <code class="filename">a.cpp</code>, but won't affect <code class="filename">foo</code>.
    </p>
<p>
      Let's improve this project further. The library probably has some headers
      that must be used when compiling <code class="filename">app.cpp</code>. We could
      manually add the necessary <code class="computeroutput">#include</code> paths to
      <code class="filename">app</code>'s requirements as values of the
      <code class="varname">&lt;include&gt;  </code> feature, but then this work will be
      repeated for all programs that use <code class="filename">foo</code>. A better
      solution is to modify <code class="filename">util/foo/Jamfile</code> in this way:

      </p>
<pre class="programlisting">
project
    <span class="special">:</span> usage-requirements &lt;include&gt;.
    <span class="special">;</span>

lib foo <span class="special">:</span> foo.cpp <span class="special">;</span></pre>
<p>

      Usage requirements are applied not to the target being declared but to its
      dependants. In this case, <code class="literal">&lt;include&gt;.</code> will be
      applied to all targets that directly depend on <code class="filename">foo</code>.
    </p>
<p>
      Another improvement is using symbolic identifiers to refer to the library,
      as opposed to <code class="filename">Jamfile</code> location. In a large project, a
      library can be used by many targets, and if they all use <code class="filename">Jamfile
      </code> location, a change in directory organization entails much
      work. The solution is to use project ids&#8212;symbolic names not tied to
      directory layout. First, we need to assign a project id by adding this
      code to <code class="filename">Jamroot</code>:
    </p>
<pre class="programlisting">
use-project /library-example/foo <span class="special">:</span> util/foo <span class="special">;</span></pre>
<p>
      Second, we modify <code class="filename">app/Jamfile</code> to use the project id:
      </p>
<pre class="programlisting">
exe app : app.cpp /library-example/foo//bar ;</pre>
<p>

      The <code class="filename">/library-example/foo//bar</code> syntax is used to refer
      to the target <code class="filename">bar</code> in the project with id <code class="filename">
      /library-example/foo</code>. We've achieved our goal&#8212;if the
      library is moved to a different directory, only <code class="filename">Jamroot
      </code> must be modified. Note that project ids are global&#8212;two
      Jamfiles are not allowed to assign the same project id to different
      directories.
    </p>
<div class="tip"><table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Tip]" src="../../../doc/src/images/tip.png"></td>
<th align="left">Tip</th>
</tr>
<tr><td align="left" valign="top">
<p>If you want all applications in some project to link to a certain
        library, you can avoid having to specify it directly the sources of
        every target by using the <code class="varname">&lt;library&gt;</code> property.
        For example, if <code class="filename">/boost/filesystem//fs</code> should be
        linked to all applications in your project, you can add
        <code class="computeroutput">&lt;library&gt;/boost/filesystem//fs</code> to the project's
        requirements, like this:
      </p>
<pre class="programlisting">
project
   <span class="special">:</span> requirements &lt;library&gt;/boost/filesystem//fs
   <span class="special">;</span></pre>
</td></tr>
</table></div>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="bbv2.tutorial.linkage"></a>Static and shared libaries</h3></div></div></div>
<p>
      Libraries can be either <span class="emphasis"><em>static</em></span>, which means they are
      included in executable files that use them, or <span class="emphasis"><em>shared</em></span>
      (a.k.a. <span class="emphasis"><em>dynamic</em></span>), which are only referred to from
      executables, and must be available at run time. Boost.Build can create and
      use both kinds.
    </p>
<p>
      The kind of library produced from a <code class="computeroutput">lib</code> target is determined
      by the value of the <code class="varname">link</code> feature. Default value is
      <code class="literal">shared</code>, and to build a static library, the value should
      be <code class="literal">static</code>. You can request a static build either on the
      command line:
      </p>
<pre class="programlisting">b2 link=static</pre>
<p>
      or in the library's requirements:
      </p>
<pre class="programlisting">lib l <span class="special">:</span> l.cpp <span class="special">:</span> &lt;link&gt;static <span class="special">;</span></pre>
<p>
    </p>
<p>
      We can also use the <code class="varname">&lt;link&gt;</code> property to express
      linking requirements on a per-target basis. For example, if a particular
      executable can be correctly built only with the static version of a
      library, we can qualify the executable's <a class="link" href="reference.html#bbv2.reference.targets.references">target reference</a> to the
      library as follows:



      </p>
<pre class="programlisting">
exe important <span class="special">:</span> main.cpp helpers/&lt;link&gt;static <span class="special">;</span></pre>
<p>

      No matter what arguments are specified on the <span class="command"><strong>b2</strong></span>
      command line, <code class="filename">important</code> will only be linked with the
      static version of <code class="filename">helpers</code>.
    </p>
<p>
      Specifying properties in target references is especially useful if you use
      a library defined in some other project (one you can't change) but you
      still want static (or dynamic) linking to that library in all cases. If
      that library is used by many targets, you <span class="emphasis"><em>could</em></span> use
      target references everywhere:

      </p>
<pre class="programlisting">
exe e1 <span class="special">:</span> e1.cpp /other_project//bar/&lt;link&gt;static <span class="special">;</span>
exe e10 <span class="special">:</span> e10.cpp /other_project//bar/&lt;link&gt;static <span class="special">;</span></pre>
<p>

      but that's far from being convenient. A better approach is to introduce a
      level of indirection. Create a local <span class="type">alias</span> target that refers
      to the static (or dynamic) version of <code class="filename">foo</code>:

      </p>
<pre class="programlisting">
alias foo : /other_project//bar/&lt;link&gt;static ;
exe e1 : e1.cpp foo ;
exe e10 : e10.cpp foo ;</pre>
<p>

      The <a class="link" href="tasks.html#bbv2.tasks.alias" title="Alias">alias</a> rule is specifically
      used to rename a reference to a target and possibly change the
      properties.

      
    </p>
<div class="tip"><table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Tip]" src="../../../doc/src/images/tip.png"></td>
<th align="left">Tip</th>
</tr>
<tr><td align="left" valign="top">
<p>
        When one library uses another, you put the second library in the source
        list of the first. For example:
        </p>
<pre class="programlisting">
lib utils <span class="special">:</span> utils.cpp /boost/filesystem//fs <span class="special">;</span>
lib core <span class="special">:</span> core.cpp utils <span class="special">;</span>
exe app <span class="special">:</span> app.cpp core <span class="special">;</span></pre>
<p>
        This works no matter what kind of linking is used. When <code class="filename">core
        </code> is built as a shared library, it is linked directly into
        <code class="filename">utils</code>. Static libraries can't link to other
        libraries, so when <code class="filename">core</code> is built as a static
        library, its dependency on <code class="filename">utils</code> is passed along to
        <code class="filename">core</code>'s dependents, causing <code class="filename">app</code>
        to be linked with both <code class="filename">core</code> and <code class="filename">utils
        </code>.
      </p>
</td></tr>
</table></div>
<div class="note"><table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../doc/src/images/note.png"></td>
<th align="left">Note</th>
</tr>
<tr><td align="left" valign="top"><p>
        (Note for non-UNIX system). Typically, shared libraries must be
        installed to a directory in the dynamic linker's search path. Otherwise,
        applications that use shared libraries can't be started. On Windows, the
        dynamic linker's search path is given by the <code class="envar">PATH</code>
        environment variable. This restriction is lifted when you use
        Boost.Build testing facilities&#8212;the <code class="envar">PATH</code> variable
        will be automatically adjusted before running the executable.
        
      </p></td></tr>
</table></div>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="bbv2.tutorial.conditions"></a>Conditions and alternatives</h3></div></div></div>
<p>
      Sometimes, particular relationships need to be maintained among a target's
      build properties. For example, you might want to set specific <code class="computeroutput">
      #define</code> when a library is built as shared, or when a target's
      <code class="computeroutput">release</code> variant is built. This can be achieved using
      <em class="firstterm">conditional requirements</em>.

      </p>
<pre class="programlisting">
lib network <span class="special">:</span> network.cpp
    <span class="special">:</span> <span class="bold"><strong>&lt;link&gt;shared:&lt;define&gt;NEWORK_LIB_SHARED</strong></span>
     &lt;variant&gt;release:&lt;define&gt;EXTRA_FAST
    <span class="special">;</span></pre>
<p>

      In the example above, whenever <code class="filename">network</code> is built with
      <code class="computeroutput">&lt;link&gt;shared</code>, <code class="computeroutput">&lt;define&gt;NEWORK_LIB_SHARED
      </code> will be in its properties, too. Also, whenever its release variant
      is built, <code class="computeroutput">&lt;define&gt;EXTRA_FAST</code> will appear in its
      properties.
    </p>
<p>
      Sometimes the ways a target is built are so different that describing them
      using conditional requirements would be hard. For example, imagine that a
      library actually uses different source files depending on the toolset used
      to build it. We can express this situation using <em class="firstterm">target
      alternatives</em>:
      </p>
<pre class="programlisting">
lib demangler <span class="special">:</span> dummy_demangler.cpp <span class="special">;</span>                      <span class="comment"># alternative 1</span>
lib demangler <span class="special">:</span> demangler_gcc.cpp <span class="special">:</span> &lt;toolset&gt;gcc <span class="special">;</span>   <span class="comment"># alternative 2</span>
lib demangler <span class="special">:</span> demangler_msvc.cpp <span class="special">:</span> &lt;toolset&gt;msvc <span class="special">;</span> <span class="comment"># alternative 3</span></pre>
<p>
      When building <code class="filename">demangler</code>, Boost.Build will compare
      requirements for each alternative with build properties to find the best
      match. For example, when building with <code class="computeroutput">&lt;toolset&gt;gcc</code>
      alternative 2, will be selected, and when building with
      <code class="computeroutput">&lt;toolset&gt;msvc</code> alternative 3 will be selected. In all
      other cases, the most generic alternative 1 will be built.
    </p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="bbv2.tutorial.prebuilt"></a>Prebuilt targets</h3></div></div></div>
<p>
      To link to libraries whose build instructions aren't given in a Jamfile,
      you need to create <code class="computeroutput">lib</code> targets with an appropriate
      <code class="varname">file</code> property.  Target alternatives can be used to
      associate multiple library files with a single conceptual target. For
      example:
      </p>
<pre class="programlisting">
<span class="comment"># util/lib2/Jamfile</span>
lib lib2
    <span class="special">:</span>
    <span class="special">:</span> &lt;file&gt;lib2_release.a &lt;variant&gt;release
    <span class="special">;</span>

lib lib2
    <span class="special">:</span>
    <span class="special">:</span> &lt;file&gt;lib2_debug.a &lt;variant&gt;debug
    <span class="special">;</span></pre>
<p>

      This example defines two alternatives for <code class="filename">lib2</code>, and
      for each one names a prebuilt file.  Naturally, there are no sources.
      Instead, the <code class="varname">&lt;file&gt;</code> feature is used to specify
      the file name.
    </p>
<p>
      Once a prebuilt target has been declared, it can be used just like any
      other target:

      </p>
<pre class="programlisting">
exe app <span class="special">:</span> app.cpp ../util/lib2//lib2 <span class="special">;</span></pre>
<p>

      As with any target, the alternative selected depends on the properties
      propagated from <code class="filename">lib2</code>'s dependants. If we build the
      release and debug versions of <code class="filename">app</code> will be linked
      with <code class="filename">lib2_release.a</code> and <code class="filename">lib2_debug.a
      </code>, respectively.
    </p>
<p>
      System libraries&#8212;those that are automatically found by the toolset
      by searching through some set of predetermined paths&#8212;should be
      declared almost like regular ones:

      </p>
<pre class="programlisting">
lib pythonlib <span class="special">:</span> <span class="special">:</span> &lt;name&gt;python22 <span class="special">;</span></pre>
<p>

      We again don't specify any sources, but give a <code class="varname">name</code>
      that should be passed to the compiler. If the gcc toolset were used to
      link an executable target to <code class="filename">pythonlib</code>,
      <code class="option">-lpython22</code> would appear in the command line (other
      compilers may use different options).
    </p>
<p>
      We can also specify where the toolset should look for the library:

      </p>
<pre class="programlisting">
lib pythonlib <span class="special">:</span> <span class="special">:</span> &lt;name&gt;python22 &lt;search&gt;/opt/lib <span class="special">;</span></pre>
<p>

      And, of course, target alternatives can be used in the usual way:

      </p>
<pre class="programlisting">
lib pythonlib <span class="special">:</span> <span class="special">:</span> &lt;name&gt;python22 &lt;variant&gt;release <span class="special">;</span>
lib pythonlib <span class="special">:</span> <span class="special">:</span> &lt;name&gt;python22_d &lt;variant&gt;debug <span class="special">;</span></pre>
<p>
    </p>
<p>
      A more advanced use of prebuilt targets is described in <a class="xref" href="faq.html#bbv2.recipies.site-config" title="Targets in site-config.jam">the section called &#8220;Targets in site-config.jam&#8221;</a>.
    </p>
</div>
<div class="footnotes">
<br><hr width="100" align="left">
<div class="footnote"><p><sup>[<a id="ftn.idp211870528" href="#idp211870528" class="para">13</a>] </sup>
             See <a class="xref" href="reference.html#bbv2.reference.features.attributes" title="Feature Attributes">the section called &#8220;Feature Attributes&#8221;</a>
          </p></div>
<div class="footnote"><p><sup>[<a id="ftn.idp211886336" href="#idp211886336" class="para">14</a>] </sup>Many
      features will be overridden,
      rather than added-to, in subprojects.  See <a class="xref" href="reference.html#bbv2.reference.features.attributes" title="Feature Attributes">the section called &#8220;Feature Attributes&#8221;</a> for more
      information</p></div>
</div>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright &#169; 2006-2009 Vladimir Prus<p>Distributed under the Boost Software License, Version 1.0.
      (See accompanying file <code class="filename">LICENSE_1_0.txt</code> or copy at 
      <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
      </p>
</div></td>
</tr></table>
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